On the Cover: The Sun has set on Mars, but twilight lingers, casting a reddish glow on the Martian surface (left) and the top of Viking Lander 1 (right). Red dust in the atmosphere scatters the sunlight, producing the color of the sunset. The coloured rings in the sky are not real; they are artifacts of severe contrast enhancement produced by computer processing of the camera's transmitted image. JPL/NASA
3 The Last Viking: Long-time science journalist Jonathan Eberhart gives a poetic summary of the Viking mission to Mars.